Network security is an on-going issue for users of public and private networks. Virtual Private Networks (VPN) can be used to extend a private network over the Internet to allow a remote user to access the private network for example. Typically once the remote user has negotiated the firewall, the user then has full access to the private network. Similarly users connected within the private network typically also have full access to this network, or their access is restricted based on security provisions installed at individual resources within the private network.
Distributed private networks such as wide area networks (WAN) typically use leased lines to couple geographically distant local area networks (LAN), however this is expensive an typically requires co-ordinated setting of the firewall rules at each site which can be complex and may diverge over time due to differing local requirements and leading to connection difficulties.